The present invention relates to a nano-scale corrosion resistant composite material, especially to a of epoxy/modified silicon dioxide nanocomposite that is gas resistant and corrosion resistant for being applied to optoelectronics, fire-retardant materials, food packaging materials, corrosion resistant materials or other fields for corrosion prevention.
When chemical reaction occurs on metal surface and turns the metal into metal oxide, the metal properties such as metallic shine, mechanical strength, physical property and chemical property change and this is called corrosion. When metal surface contacts with air, oxide and water in the air reacts with iron to produce rust, reacts with copper to generate patina, or reacts with silver to generate black metal oxide. The cost for replacing part or total corrupted metal and the cost for coping with corrosion per year all over the world is billions. Thus metal corrosion has become an important issue. The corrosion speed of metal depends on environmental conditions. However, no matter the speed is quick or slow, the metal corrosion is closely related to materials on surroundings because the corrosion is caused by contact between metal and environmental materials. The content of corrosion varies under different environments.
A research in 1998 pointed that the cost of loss caused by metal corrosion is about 4.9% of Gross Domestic Product. The loss caused by corrosion is dramatically higher than loss due to flood, fire and earthquake. Only corrosion related to cars leads to loss over 16 billions. Moreover, corrosion also cause waste of resources. About 40% of steel produced by all steel plants is used to replace the corroded metal. Iron is the most common used metal and occupies 90% of the total production of metal. In the future, the demand of steel still keeps growing. Through smelting operation, iron oxide is reduced to generate iron and steel. Thus there is a tendency of metals to easy to revert back to their ore form. For example, cast iron forms reddish-brown iron oxide—this is called rusting. Especially Taiwan locates in the subtropical zone and the environment is high-temperature, high-humidity and high salinity, both create a place for corrosion. Although a large amount of plastic is used to prevent corrosion, iron and steel are still indispensable materials for modern industries due to their easy processing, low cost and recyclability.
There are a plurality of ways to prevent metal corrosion such as surface treatment, plating, corrosion inhibitor, electro-protection, thermal spray, coating etc. The most economic and convenient way painting. This way is applied broadly to maintenance of steel structure. For example, Golden Gate Bridge, a landmark construction of San Francisco is protected mainly by coating.
By coating, an evenly membrane is formed on surface of material so as to isolate possible factors that cause corrosion such as air and water. In order to prevent corrosion, conventional way is to paint red lead, zinc chromate, strontium chromate, and calcium plumbate as a base layer. Yet these paints all include heavy metal that causes pollution. At the same time, these pollutants are carcinogens and result in other diseases so that they are prohibited gradually.
The most common way to prevent corrosion is to effectively isolate metal with environmental factors that cause corrosion. Generally, there are three ways for corrosion protection and prevention—electro-protection, coating, and corrosion inhibitor. In electrochemistry field, a plurality of corrosion protection ways are applied such as painting, plating, phosphating, anodizing, metallic coating protection, nonmetallic coating protection, and electro-protection. The painting way uses organic coatings. As to research of anticorrosive coating materials, organic conjugated conducting polymer such as polyaniline is the most perspective. Due to reversible chemical structure, it induces a passive oxide layer on metal surface so as to reduce corrosion effectively. Thus quite a lot scientists are dedicated to the research in this field.
While applying conventional anticorrosive primer or paint, rust removing on metal surface should be done completely. Otherwise during dead time of painting, metal surface contacts with air and have oxidation reaction immediately. Moreover, conventional rust-preventing primer such as red lead, zinc chromate, inorganic zinc coating, aluminium phosphate, and resins can only cover on surfaces. After a period of time, oxygen and water molecule penetrate the covering membrane and the metal surface is oxidized within a few months. Thus it's impossible to remove rust completely and coatings (paintings) should be applied often so as to maintain corrosion protection effect.
In recent years, a plurality of research projects is conducted on organic/inorganic nanocomposites. A lot of papers related to epoxy/TS nanocomposites are presented. The published liter shows that the research of epoxy/TS nanocomposites performing now focuses on their synthesis, identification, reaction mechanism, thermal properties and mechanical properties. However, gas barrier property and corrosion control are seldom mentioned about.
Conventional corrosion resistant coating has many disadvantages such as heavy metal therein that leads to pollution and works as carcinogen, and high cost of repeated painting at certain intervals for maintaining corrosion prevention. Therefore, there is a need to provide a novel epoxy/TS nanocomposites with properties of gas barrier (oxygen and water) and corrosion protection for being applied to corrosion prevention of optoelectronics or other fields.